Electrical connector



United States Patent Inventors John J. Bahen, Jr.;

George F. Swenck; Jesse B. Thomas, Henrico County, Va.

July 16, 1968 Dec. 15, 1970 Reynolds Metals Company Richmond, Va.

a corporation of Delaware Appl. No. Filed Patented Assignee ELECTRICALCONNECTOR 13 Claims, 6 Drawing Figs.

U.S. Cl 174/13, 174/28, 174/88 Int. Cl H01b 9/06 Field ofSearch 174/13,14, 28, 29,15C, 883, 21.4, 99E; 339/9E References Cited UNITED STATESPATENTS 5/1930 Dibner 339/9(E) 7/1932 Affel 174/14 7/1934 VanSplunter... 339/9(E) 12/1963 Kuehl et al 174/12X 6/1967 Lear l74/88(B)3/1968 Sewell l74/28X FOREIGN PATENTS 6/1889 Great Britain... 174/134/1949 France l74/21.4 6/1949 France 174/2l.4

Primary ExaminerLewis H. Myers Assistant Examiner-A. T. GrimleyAttorney-Glenn, Palmer, Lyne, Gibbs & Thompson ABSTRACT: A connector forelectrically connecting associated ends of a pair of elongatedelectrical conductors while allowing relative movement therebetween andan electrical power transmission system using such connector.

PATENT EU nun 519m SHEET 1 BF 3 INVENTORS BAHEN JOHN J. ,JR.

GEORGE F. SWENCK JESSE B. THOMAS mama,

THEIR ATTORNEYS PATENTED DEE! I970 SHEET 2 OF 3 INVENTORS JOHN J, BAHENJR. GEORGE E swENcK BY JESSE B. THOMAS & M 6 wo wa/ QM 2. ow mm EN .23mm N@ E 8 A m mm V 3% A Q m? VN; |v Q .IJ @v L Hi 1 i 0. I1 v, 8 G Rpm Lr NR5 K E m x NN Q QKow THEIR ATTORNEYS PATENTEUBEcT 5 I976 SHEET 3 [IF3 qwv T 9.

INVENTORi JOHN J. BAHEN J F. swENcK B. THOMAS 210m (f/Z-Zam) THEIRATTORNEYS GEORGE JESSE ELECTRICAL CONNECTOR BACKGROUND OF THE INVENTIONElectrical power transmission conductors used transmit electrical powerover great distances are subject to a wide range of temperatures causinglarge expanding and contracting movements thereof. In undergroundsystems, for example, the conductors must be supported laterally withinconfined limits and such conductors expand and contract comparativelylarge amounts along their lengths. Accordingly, it is necessary toprovide suitable connectors, commonly referred to as expansion joints,between adjoining end-to-end underground conductors to compensate forthe large amounts of longitudinal expansion and contraction mentionedabove. Each of the previously proposed expansion joints usedin'association with housed conductors is deficient in one or more of thefollowing respects in that it is too expensive to produce and install,occupies too much space, does not provide an adequate current carryingcapacity across the expansion joint, and has great rigidity whichresults in heavy loads in an associated system due to expansion andcontraction.

SUMMARY This invention provides an improved connector, i.e., expansionjoint, for electrically connecting associated ends of a pair ofelongated electrical conductors which is of simple and economicalconstruction, occupies a comparatively small volume, providesconductivity which is no less than the conductivity of its associatedelectrical conductors, and is com paratively freely expandible andcontractible in response to contraction and expansion of its associatedelectrical conductors. This invention also provides an improved housedelectrical power transmission system which provides efficient electricalpower transmission while substantially eliminating undue stresses in theend-to-end electrical conductors relative to their associated protectiveconduit or housing.

Other details, uses, and advantages of this invention will becomeapparent as the following description of the exemplary embodimentsthereof presented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings showexemplary embodiments of this invention, in which FIG. 1 is a view withparts in section and parts broken away illustrating a plurality ofelectrical v conductors suitably fastened in end-to-end relation andwith an exemplary expansion joint of this invention fastened in positionbetween each adjoining pair of electrical conductors and illustratingsuch conductors and expansion joints carried within an associatedprotective conduit of the type used in housed power transmissionsystems;

F IG. 2 is an exploded perspective view with parts in section and partsbroken away particularly illustrating the component parts of theexemplary electrical-expansion joint of FIG. 1;

FIG. 3 is an enlarged cross-sectional view with parts broken awayparticularly illustrating the expansion joint of FIG. 1 installed inposition between a pair of associated electrical conductors and showingtwo types of spacers which may be used to support an electricalconductor substantially centrally within is associated protectiveconduit;

FIG. 4 is a view taken on the line 4-4 of FIG. 3 particularlyillustrating the arcuate configuration of the outwardly extending legsof a plurality of outer U-shaped leads comprising the expansion joint ofFIG. 1;

FIG. 5 is an enlarged cross-sectional view with parts broken awayillustrating another exemplary embodiment of the expansion joint of thisinvention; and

FIG. 6 is a view taken on the line 6-6 of FIG. 5.

DESCRIPTION OF ILLUSTRATED EMBODIMENTS Reference is now made to FIG. 1of the drawings wherein one exemplary embodiment of an electrical powertransmission system of this invention is illustrated and designatedgenerally by the reference numeral 20. The power transmission system 20may be used in any application where it is desired to transmitelectrical power through housed conductors and comprises an outerprotective conduit or housing which is designated generally by thereference numeral 21 and is defined by a plurality of substantiallyidentical cylindrical conduit sections 22 and a plurality of cooperatingcomparatively large diameter cylindrical sections 23 suitably fixed inposition at predetermined intervals and such comparatively largediameter cylindrical portions 23 are adapted to receive an expansionjoint of this invention therewithin.

The sections 22 and 23 of conduit 21 may be fastened together in anysuitable manner so as to provide a fluidtight connection therebetween;however, in this example of the invention such conduit sections areshown as being welded together so as to provide a fluidtight connectionof high quality and optimum structural strength between adjoiningconduit sections and a representative few of such welds have beendesignated by the same reference numeral 24 in FIG. 1 of the drawings.

The exemplary electrical power transmission system 20 shown in FIG. 1has a plurality of elongated electrical conductors 26 carried within theconduit 21 and each conductor 26 of this example of the invention has acylindrical configuration. The power transmission system 20 uses anembodiment of an electrical expansion joint which is designatedgenerally by the reference numeral 30 and provided for electricallyconnecting associated ends of each pair of electrical conductors 26.

The power transmission system 20 has a plurality of electricalinsulating spacers 31 fixed to each electrical conductor 26 at spacedintervals and the spacers support their associated lead within theconduit 21 while allowing axial sliding movement of the electricalconductors 26 within the conduit 21. The power transmission system 20also has a plurality of dualpurpose spacers 32; and, in this example ofthe invention each dual-purpose spacer is fixed to an associatedelongated electrical conductor 26 along the central portion thereof.Each dualpurpose spacer 32 supports its associated conductor 26 within Ithe conduit 21 in a similar manner as each spacer 31; however, eachspacer 32 is also anchored or fixed to the conduit 21 as shown at 33 toassure that axial expansion and contraction of the associated conductor26 due to temperature changes occurs only on opposite sides of thedual-purpose spacer 32 to thereby prevent the associated conductor 26from creeping or walking axially along the conduit 21.

The spacers 31 and 32 are made of an electrical insulating material soas to electrically insulate the conductors 26,from the conduit 21.Further, each spacer 31 and 32 may be fixed to its associated electricalconductor 26 in any suitable manner such as by a suitable cement, bywelding a bead adjacent each side of each spacer 31 and 32 and as shownat 34, or by fixing a pair of annular bands to an associated conductor26 and on opposite sides of a particular spacer, for example.

Each dual-purpose spacer 32 of this example of the invention is attachedor anchored axially along conduit 21 by welding a pair of annularflanges 35, see FIG. '3, adjacent associated terminal ends of a pair ofconduit sections 22 which are to be placed in abutting end-to-endrelation. The conduit sections 22 with their flanges 35 fixed inposition are then placed together as shown at 36 so that an associatedspacer 32 is sandwiched between the flanges 35 whereupon the abuttedends of conduit sections are welded together to thereby fix the centralportion of the associated conductor 26 within the housing 21 to preventexcessive creeping or walking of the conductor in wither directionwithin the conduit 21.

The power transmission system 20 utilizing the exemplary expansion joint30 preferably utilizes an electrically nonconductive (i.e., electricalinsulating) fluid such as an inert gas, fon example, under pressurewhich is carried within the conduit 21 so that it fills the volumebetween each electrical conductor 2 6 and expansion joint 30 and theoutside conduit 21. This utilization ofaninert gas under pressure helpsto assure the provision of maximum electrical insulation along the fulllength of 'eaelielectrical conductor 26. Further, the use of anelectrical insulating fluid also serves to' dissipate heat away from theconductors'26 and expansion joints 30 and thereby helps to cool thesecomponents.

To assure that the inert gas indicated by the reference numeral at 37 inFIGS. 1 and 3 is free to flow along the full length of the conduit 21each spacer 31 and 32 has a plurality of openings 38 and 39 respectivelyprovided therein and the Having described in general terms theelectrical power transmission system with its conduit 21, electricalconductors 26, spacers3l and 32, and expansion joints 30 betweeneachadjoining pair of conductors 26,the' description will now proceedwith a detailed description of the exemplary expansion joint 30illustrated'in FIG. 1.

The expansion joint 30 comprises a pair of spaced circular v plates orsupports 40 each fixed to an associated electrical conductor 26 throughthe use of a transition member 41. Each f juplate 40. has a plurality ofopenings 42 provided therein and the openings 42 are arranged inwardlyof its peripheral outline f indicated at 43. The plates 40 of thisexampleof theinvention are substantially identical and the openings 42in one plate 40 are arranged opposite corresponding openings 42 in theother 1 plate so as to define a plurality of cooperating sets or pairsof openings in such plates. Further, each cooperating set of openings isarranged so that a straight line through the center 5, of each set isarranged parallel to the central axis of the expansion joint 30.

The expansion joint 30 also has a plurality of substantially U-shapedaxially flexible electrical leads 45 extending f between the plates 40and the leads 45 have the same length.

QEach substantially U-shaped lead 45 has identical opposite -leridportions 46 which are arranged inaligned relation on a ,Icommon axis,i.e., end portions 46 are arranged in a rectilinear path. Each U-shapedlead also has a bight 48 and a 'Qpair of substantially parallel legs 47extending outwardly etherefrom and the end portions 46 extend inopposite {directions from the terminal outer ends of the legs 47. The op;-,posite end portions 46 extend through an associated set of;.,cooperating openings 42 in the plates 40 and each' end portion l46isfixed to its associated plate so that with movement of the ,pla'tes 40toward and away form each other the U-shaped leads 45 deflect or flex tocompensate for movement of the {plates 40. i

5 Each of the plates 40 has its openings 42 formed therein so {that theyarearranged on a plurality of concentric circles and in this example ofthe invention a plurality of three concentric circles designatedgenerally by the reference numerals 50, 51

and 52 are illustrated. If desired, the openings 42 in each plate ,40may be arranged so that a radial line extending from the .center of theconcentriccircles 50-52 outwardly along the plate 50 will not intersectopenings 42 provided in two im- .tnediately adjacent concentric circlesto thereby assure maxv,fimum spacing is provided between eachimmediately adjacent pair of'openings 42 arranged on differentconcentric circles. W The plates 40 illustrated in this example of theinvention have a circular peripheral outline and each plate has' a com-I parativel y large central opening 55 extending therethrough vanddefined by a substantially right circular cylindrical surface 56. Aspreviously mentioned the U-shaped leads 45 have the same overall lengthand such leads have all been designated by .the'reference numeral 45 forconvenience and ease of presentation; however, it will be appreciatedfrom FIGS. 2 and 3 of the drawings and the presentation to be madesubsequently that although all of the leads 45 have similarconfigurations, all leads 45 do not have identical configurations.

The U-shaped leads 45 are fixed at their opposite ends 46 to the plates40 so that the bight 48 of each lead 45 extends toward the outerperiphery, i.e., circumference 43 of the circular plates 40. TheU-shaped leads 45 associating with openings 42 arranged on theinnermost'concentric circles 50 each have a narrow bight 48 andcomparatively long end portions 46. The U-shaped leads 45 associatingwith the outermost concentric circles 52 each have a comparatively widebight 48 and comparatively short end portions 46. Similarly, theintermediate U-shaped leads 45 associating with the interl mediateconcentric circles 51 each have a bight 48 of intermediate width and endportions 46 of intermediate length.

With this arrangement it will be seen that a maximum number of U-shapedelectrical leads 45 thatare axially flexible are provided between theplates to, in effect, provide an axially flexible electrical expansionjoint 30 wherein 'the combined conductivity or current carrying capacityof the U- shaped leads is not less than that of each conductor 26. Infact, the combined conductivity of the .U-shaped leads 45 is generallygreater than the conductivity ofeither of the conductors 26 so as toprovide an electrical connection providing optimum performance.

From the illustration presented in FIGS.v 2-4 of the drawings, it willalso be seen that the size and arrangement of the plates 40 and U-shapedleads 45 enable the provision of flexible leads having maximum lengthfor easy flexing yet in a comparatively small volume as determined bythe circumference 43 of each plate 40 and the distance between suchplates. To help assure that each substantially U-shapedlead 45 has amaximum length and therefore is easier to flex, the outwardly extendinglegs 48 of each U-shaped lead are preferably arranged to extend in anarcuate path as illustrated at 60, see FIG. 4, for a typical U-shap'edlead 45. Only the Ushaped leads 45 associating with the outer concentriccircles 52 are illustrated as extending in an arcuate path in FIG. 4 ofthe drawings; however, it will be appreciated that all of the electricalleads 45 may have their leg portions 48 similarly arranged. Further,each U-shaped lead 45 associating with a given concentric circle willpreferably have'its bight 48 arranged at a different radial positionthan the bight 48 of a U-shaped lead 45 associating with an immediatelyadjacent concentric circle whereby maximum spacing may be providedbetween the U- shaped leads 45 comprising the expansion joint 30.

The U-shaped leads 45 are fixed to their associated circular plates 40after first extending their opposite end portions 46 through associatedopenings 42 in the supports or plates 40. The outside diameter of eachend portion 46 is correlated to the diameter of an associated opening 42to provide a snug fit between each end portion 46 and its associatedplate 40. This snug fit enables the U-shaped leads 45 to be positionedso that the bight 48 of each U-shaped lead 45 is arranged and held atthe desired position without requiring special holding fixtures, or thelike, prior to fixing the U-shaped leads 45 to the plates 40.

Any suitable technique may be used to fix the end portions 46 of theU-shaped leads 45 in position against each associatedplate; however, onetechnique which has been successfully utilized is to weld each outer endportion 46 of each U-shaped lead 45 to its associated plate 40 asindicated at 62 in FIG. 3.

Reference is now made to FIG. 2 of the drawings for a detailedpresentation of the transition members 41 and the manner of attachingmembers 41 in position. Each transition member 41 of the exemplaryexpansion joint30 has a substantially frustoconical configuration andhas an inner end portion 64 which corresponds in peripheral outline toits associated electrical conductor 26. Each conductor 26 has a taperedend portion 65 which is arranged, i.e., abutted, against the end portion64 and suitably fixed thereto. In this example of the invention theconductor 26 is preferably welded to transition member 41 by a weld 66between tapered end portion 65 of conductor 26 and inner end portion 64of the transition member 41.

Each transition member 41 also has a comparatively large diameter outerend portion67 and the large diameter outer end portion 67 of eachtransition 41 has an annular planar surface 68 which is placed againstan associated plate 40 and welded in position and as indicated at 71inFIG. 3. The small inside diameter portion 72 of annular planar surface68 is arranged against its associated plate 40 so that it is positionedoutwardly of the outermost of the concentric circles 52 previouslydescribed. This arrangement assures that the end portions 46 of theU-shaped electrical leads 45 associating with the openings 42 arrangedin the outer concentric circles 52 do not interfere with the placementof annular surface 68 against the outer planar surface of an associatedplate 40.

Each transition member 41 also has a central cylindrical projection 73which corresponds in configuration to the central aperture 55 providedin an associated plate 40. The central projection 73 enables theassociated transition member 41 to be installed and centered in positionagainst cylindrical surface 56 of an associated plate 40 to enablewelding thereof at a precise position. Each 'member 41 is ofsubstantially frustoconical configuration, as previouslyindicated, andhas an aperture 74 extending axially therethrough. The projection 73 andannular surface 68 previously described is defined by providing a cutoutportion 75 in the large diameter inner end portion 67 of member 41.Further, the terminal end portion of projection 73 extends outwardly ofthe planeof the annular planar surface 68 as indicated at 76 so as'toprovide the centering action described above. Thus, it is seen that theexpansion joint 30 has identical transition. members 41 fastened toplates 40 arranged at its opposite ends and U-shaped leads 45 extendingbetween the plates 40 so that an integral unit of comparatively smalloutside peripheral outline, i.e. diameter, is provided which iscomparatively easy to flex axially yet has optimum structural integrityand current carrying capacity.

The connector 30 also has a .cylindrical anticorona discharge shield 80suitably fastened .in position around the circular plates 40. Each ofthe circular plates 40 has an annular groove 81 provided therein so thatit extends radially inwardly toward the center of the plate 40.

The shield 80 has an annular fasteningprojection 82 adjacent one endwhich is received within an associated annular groove 81 of one plate 40so as to fasten" the associated end of the shield 80 in position. Theannular groove 81 provided in the oppositely arranged plate 40 has anantifriction annular ring such as a Teflon ring 83 and the ring83-provides wear resistance between the shield 80 and its associatedplate 40.

During the expansion and contraction of the electrical conductors'26there is a tendency for the circular plates 40 to move toward and awayfrom each other. With the cylindrical shield 80 fastened to one of theplates 40 the shield 80 is free to slide across the ring 83 in anunrestrained manner.

In the exemplary embodiment of this invention illustrated in FIGS. 1-4of the drawings the conductors 26 and expansion joints 30 may be made toany suitable electrically conductive material. Further, the outerprotective conduit'2l with its con duit sections 22 and 23 may be madeof any suitable protec- 6 tive material either metallic or nonmetallic.In particular, conductors made of EC 1 100 or 6201 aluminum alloys havebeen successfully utilized and wherein the tubular conductors 26 had anoutside diameter of 3 inches and an inside diameter of l b inches. Theshield 80 may also be made of the aluminum alloys such as EC 1100, 6061or 3003; and, outer protective conduits made of 6063-T4 aluminum alloyhave been successfully utilized.

The U-shaped leads 45 may be uninsulated or electrically insulated alongtheir full lengths except at their outer end portions 46 where they areelectrically connected to their associated plates 40. Also, any desirednumber and arrangement of leads 45 may be used between associated plates40. The exemplary expansion joint 30 illustrates a plurality of 54 U-shaped leads merely by way of example and, as previously indicated, theleads 45 have a combined total conductivity which is equal to or greaterthan the conductivity of each conductor 26.

It will be appreciated that different materials may be used to make theelectrical conductors 26 and electrical leads 45, accordingly acomparison between the leads 45 and conductors 26 has been expressed inthis specification in terms of combined total conductivity or currentcarrying capacity of the leads 45 as compared with the conductivity orcurrent carrying capacity of the conductors 26. Further, each lead 45may be made of a single wire or of a plurality of wires suitably bunchedtogether.

Another exemplary embodiment of this invention is illustrated in FIGS. 5and 6 of the drawings wherein the expansion joint illustrated is verysimilar to the expansion joint 30; therefore, the expansion joint ofFIGS. 5 and 6 willbe designated generally by the reference numeral 30Aand its component parts which are similar to corresponding parts of theexpansion joint 30 will be designated by the same numeral as in theexpansion joint 30 also followed by the letter designation A and notdescribed again. Only those component parts which are substantiallydifferent from corresponding parts of the expansion joint 30 will bedesignated by a new reference numeral also followed by the letterdesignation A and described in detail.

The exemplary expansion joint 30A has a pair of identical transitionmembers A which serve the same function as the transition members 41 ofthe expansion joint 30. Each transition member 90A has a small diametercylindrical inner portion 91A which is arranged in telescoped relationover an associated electrical conductor 26 and suitably welded inposition as indicated at 92A. Each transition member 90A also has alarge diameter cylindrical portion 93A which is telescoped over thesmall diameter cylindrical portion 91A as indicated at 94A and fixedthereto in any suitable manner (such as explosive bonding, for example)so as to define a high quality electrical and mechanical connectiontherebetween. The terminal outer end of the large diameter cylindricalportion 93A may be welded to its associated plate 40A as shown at 71A.

The exemplary expansion joint 30 illustrated in FIGS. l4 of the drawingsis shown as having its U-shaped leads arranged to extend between aplurality of three concentric circles 50- 52 in each plate 40. However,the expansion joint 30A shown in FIGS. 5 and 6 has its U-shaped leads45A arranged to extend between a plurality of only two concentriccircles in each plate 40A and the innermost concentric circle isdesignated by the reference numeral 50 A, see FIG. 6, while theoutermost concentric circle is designated by the reference numeral 52A.

The openings 42A in each plate 40A are of noncircular cross-sectionaloutline and the cross-sectional outline of each U-shaped lead 45A isalso made to correspond to the crosssectional outline of each opening42A. In particular, the openings 42A are of substantially ellipticaloutline while the end portions 46A of each lead 45A are of acorresponding elliptical cross-sectional configuration. However, it isto be understood that the openings 42 and 42A in plates 40 and 40A ofexpansion joints 30 and 30A respectively may have any desiredconfiguration with the associated U-shaped leads having a correspondingconfiguration in each instance.

The expansion joint 30A is very similar to the expansion joint 30 andserves an identical purpose of allowing relative movement between a pairof adjoining electrical conductors 26; Each expansion joint 30 and 30Ahas optimum structural integrity and a plurality of U-shaped leads whichin each expansion joint have a combined total conductivity which isequal to or greater than the conductivity of the conductors 26. Further,each expansion joint 30 and 30A occupies a minimum amount of space orvolume while enabling comparatively easy axial flexing thereof withouttending to buckle the associated electrical conductors in eachparticular instance.

Although specific configurations have been illustrated for thetransition members 41 and 90A of expansion joints 30 and 30Arespectively, it will be amciated that such configurations may bemodified to provide easier attachment of chill blocks which may be usedduring welding of each transition member in position. Also, theparticular configuration of a given expansion joint 30 or 30A may bemodified to improve the electrical properties thereof so as to minimizecorona 1 discharge effects.

. such force is substantially smaller than the force required to The;cross-sectional area and configuration of each of the leadslQS and 45Aof expansion joints 30 and 30A respectively "is'preferably determined bytest so as to establish the exact force required to axially move theU-shaped leads and assure buckle a particular conductor 26. Also, thetemper of each U- shaped lead is such as to provide the best fatigueproperties.

The exemplary expansion joints 30 and 30A are shown as well as theperipheral outline of the central portion of such ,given expansion jointmay have any desired configuration such j as elliptical, for example.

it will also be seen that the outer protective conduit 21 for .1 thehoused" system presented-in this specification has comqparatively smalldiameter tubular sections 22 and larger diameter. sections 23 suitablyfixed together in end-to-end relation. The outside diameter of eachsection 23 is dimensioned so that it provides adequate radial clearancesurrounding its associatedexpansion joint. However, it is to beunderstood that the actual overall size of a particular expansion 5joint and configuration and size of tubular sections 22 may be 'suchthat the outer conduit 21 may be comprised solely of #end-to-endsections 22 without requiring that the larger sections 23 be utilized.

' The electrical power transmission system of this invention 'with itshoused electrical conductors and expansion joints may fiibe used abovegroundas well as underground and under .water.

While present exemplary embodiments of this invention, and methods ofpracticing the same, have been illustrated and fdescribed, it will berecognized that this invention may be otherwise variously embodied andpracticed within the scope of the following claims.

' We claim: 1. An expansion joint for electrically connecting associatedends of a pair of elongated electrical conductors while allowingrelative movement therebetween, said expansion joint comprising, a pairof spaced apart supports each fixed to an "associated one of saidelectrical conductors, a plurality of openingslin each support, saidopenings being arranged inwardly of the peripheral outline of eachsupport and opposite corresponding openings in the other of saidsupports to define a plurality of cooperating sets of openings in saidsupports, and a plurality of substantially U-shaped axially flexibleelec- 'trical leads extending between said supports, each of said leadshaving opposite end portions extending through an associated set ofcooperating openings with each end portion being fixed to its associatedsupport so that with movement of said supports toward and away from eachother said leads flex to compensate for said movement, each of saidsupports having its openings formed therein so that they are arranged ina plurality of concentricclosed plane curves and with the bight of eachU-shaped lead being arranged to extend toward the outer periphery ofeach support, said U-shaped leads associating. with openings arranged onthe innermost of said concentr'ic closed plane curves having a narrowbight and comparatively long end portions and said U-shaped leadsassociating with openings arranged on the outermost of said concentricclosed plane curves having a comparatively wide bight and comparativelyshort end portions, said U-shaped leads being arranged to providemaximum spacing between immediately adjacent U-shaped leads, saidexpansion joint occupying a small volume yet providing a maximum numberof easily flexible electrical leads interconnected between saidelectrical conductors so that the combined current carrying capacity ofsaid leads is not less than the current carrying capacity of eachelectrical conductor.

2. An expansion joint as set forth in claim 1 in which the openings ineach of said supports are formed in a plurality of concentric closedplane curves defined as concentric circles.

3. An expansion joint as set forth in claim 2 in which each of saidsubstantially U-shaped leads has the same overalllength.

4. An expansion joint as set forth in-claim 2 in which each of saidU-shaped leads comprises a bight and a pair of outwardly extending legs,said end portions on each lead extending from opposite ones of saidoutwardly extending legs and being arranged in a rectilinear path. I

5. An expansion joint as set forth in' claim 2 in which the outwardlyextending legs of each U-shaped lead extend in an arcuate path so as toprovide maximum length therefor within a small volume and thereby enableeasier flexing of each lead within such small volume. I

6. An expansion joint as set forth in claim 2 in which, said electricalconductors are of circular peripheral outline, said supports comprise apair of substantially identical plates of circular peripheral outlinewith the circumference of each plate being substantially greater thanthe circumference of either of said electrical conductors, and furthercomprising a pair of identical transition members comprising oppositeends of each expansion joint, each transition member having an inner endcorresponding in peripheral configuration to its associated electricalconductor and being fixed thereto and an outer end portion of annular'cross-sectional area fixed to an associated plate.

7. An expansion joint as set forth in claim 6 in which each transitionmember is welded to its associated plate and electrical conductor. i V

8. An expansion joint as set forth in claim 6 in which each of saidtransition members has a frustoconical configuration.

9. An expansion joint as set forth in claim 8 in which each of saidplates has a central aperture extending therethrough and each of saidfrustoconical transition members has a central projection correspondingin configuration to the central aperture in its associated plate toenable easy centering of each transition member in position on asassociated plate.

10. An expansion joint for electrically connecting associated ends of apair of elongated electrical conductors each having a circularperipheral outline while allowing relative movement therebetween, saidexpansion joint comprising, a pair of spaced apart substantiallyidentical plates each having a circular peripheral outline with thecircumference of each plate being substantially greater than thecircumference of either of said electrical conductors, a pair ofidentical transition members comprising opposite ends of each expansionjoint, each transition member having an inner end corresponding inperipheral configuration to its associated electrical conductor andbeing fixed thereto and an outer end portion of annular cross-sectionalarea fixed to an associated plate, a plurality of openings in eachplate, said openings being arranged inwardly of the peripheral outlineof each plate and-opposite corresponding openings in the other of saidplates to define a plurality of cooperating sets of openings in saidplates, and a plurality of substantially U-shaped axially flexibleelectrical leads extending between said plates, each of said leadshaving opposite end portions extending through an associated set ofcooperating openings with each end portion being fixed to its associatedplate so that with movement of said plates toward and away from eachother said leads flex to compensate for said movement, each of saidtransition members having a small diameter cylindrical portion definingsaid inner end' portion and being arranged in telescoped relation overits associated electrical conductor and fixed thereto and having a largediameter cylindrical portion defining its outer end portion.

11. An expansion joint for electrically connecting associated ends of "apair of elongated electrical conductors each having a circularperipheral outline while allowing relative movement therebetween, saidexpansion joint comprising, a pair of spaced-apart substantiallyidentical plates each having a circular peripheral outline with thecircumference of each plate being substantially greater than thecircumference of either of said electrical conductors, a pair ofidentical transi tion members comprising opposite ends of each expansionjoint, each transition member having an inner end corresponding inperipheral configuration to its associated electrical conductor andbeing fixed thereto and an outer end portion of annular cross-sectionalarea fixed to an associated plate, a plurality of openings in eachplate, said openings being arranged inwardly of the peripheral outlineof each plate and opposite corresponding openings in the other of saidplates to define a plurality of cooperating sets of openings in saidplates, and a plurality of substantially U-shaped axially flexibleelectrical leads extending between said plates, each of said leadshaving opposite end portions extending through an associated set ofcooperating openings with each end portion being fixed to its associatedplate so that with movement of said plates toward and away from eachother said leads flex to' compensate for said movement, each of saidplates having its openings formed therein in a plurality of concentriccircles and the inside diameter of the annular cross-sectional area ofthe outer end portion of each transition member being arranged outwardlyof the outermost of said concentric circles so that upon inserting saidU-shaped electrical leads through associated openings in said platessaid outer end portions of said transition members are spaced outwardlyof said leads to assure each outer end portion of each transition memberis fixed to its associated plate without interference form said leads.

[2. An expansion joint for electrically connecting associated ends of apair of elongated electrical conductors each having a circularperipheral outline .while allowing relative movement therebetween, saidexpansion joint comprising, a pair of spaced-apart substantiallyidentical plates each having a circular peripheral outline with thecircumference of each 5 joint, each transition member having an innerend corresponding in peripheral configuration to its associatedelectrical conductor and being fixed thereto and an outer end portion ofannular cross-sectional area fixed to an associated plate, a pluralityof openings in each plate, said openings being arranged inwardly of theperipheral outline of each plate and opposite corresponding openings inthe other of said plates to define a plurality of cooperating sets ofopenings in said plates, a plurality of substantially U-shaped axiallyflexible electrical leads extending between said plates, each of saidleads having opposite end portions extending through an associated setof cooperating openings with each end portion being fixed to itsassociated plate so that with movement of said plates toward and awayfrom each other said leads flex to compensate for said movement, each ofsaid circular plates having a substantially cylindrical outer surfaceand an annular groove therein extending radially inwardly beneath saidcylindrical surface, a cylindrical anticorona discharge shield having anannular fastening projection adapted to be received within an annulargroove of one of said circular plates to fasten said shield in positionand prevent axial movement thereof relative to said one plate, saidcylindrical shield extending between said plates and outwardly beyondthe other of said plates, and an antifriction annular member carriedwithin the annular groove of the other of said circular plates tominimize wear between said shield and said other plate while allowingfree axial sliding movement of said shield relative to said other plate.

13. An expansion joint as set forth in claim 2 in which eachconcentriccircle to thereby assure provision of said maximum spacing.

